Method for positively removing a resistance element from a waveguide



March 3, 1959 METHOD FOR'POSI ITIVELY REMOVING A RESISTANCE c E.LASHOIJR 2,876,423

ELEMENT FROM A WAVEGUIDE Filed 1m. 5. 1956 816mm. Souncz A 'r-ronmsvsINVENTOR.

United States Patent METHOD FOR POSITIVELY REMOVING A RESIST- AN CEELEMENT FROM A WAVEGUIDE Clarence E. Lasho, Jr., Marion, Iowa, assignorto Collins iladio Company, Cedar Rapids, Iowa, a corporation of owaApplication November 5, 1956, Serial No. 620,558

2 Claims. (Cl. 333-98) This invention relates to waveguides and moreparticularly to the automatic changing of the frequency of a particularwaveguide.

It is well-known that the wave length of a microwave may be changed asit passes through a waveguide. This phenomenon occurs because the wavelength depends both upon the frequency of the electrical energy and thephysical dimensions of the waveguide. One well-known method of changingthe frequency of a waveguide is to introduce a resistance strip or fininto a slot in the waveguide. A resistance strip pressed into awaveguide causes the velocity of transmission along the waveguide tovary, which in turn causes the frequency to change. This fin must beaccurately positioned to correctly change the wave length of themicrowave signal. If the frequency of the microwave is to be changed bythe removal of such a fin, it must be done quickly and positively. Thisinvention is a device which will positively and quickly change the wavelength of a waveguide by removing a resistance fin from a slot in thewaveguide.

It is an object of this invention to provide a quick and positive methodof removing a resistance strip or fin in a waveguide to change thefrequency of the waveguide. It is another object of this invention toprovide for the automatic removal of a resistance strip or fin from awaveguide to change the frequency of the microwave signal associatedwith the waveguide. It is still another object of this invention toprovide an automatic means for positively and accurately removing aresistance fin from a waveguide where such automatic means is remotelycontrollable.

These and other objects of this invention will become apparent when thefollowing description is read in conjunction with the drawing in which,

Figure 1 is a perspective representation of one embodiment of thisinvention; and

Figure 2 is a detailed representation of one fuse usable in thisinvention.

Referring now to Figure l, a rectangular hollow waveguide 6 is shownwith a slot 7 cut therein. This is a longitudinal slot out along thecenter line of one broad side of the rectangular waveguide 6. This slotis normally occupied by the resistance strip or fin 8. Fin 8 is held inposition in the waveguide by the slot 7 and the springs 9. Springs 9hold the fin 8 in the slot by applying spring pressure to the structuralmember 11. These springs are connected at one end to the structuralmember 11 through the holes 12. Supporting the other end of the springsis a box-like member 13 and an arm 24 attached thereto. The box-likeelement or member 13 is removably connected to a supporting unit on thewave guide. This supporting unit includes the arm 14 and necessarystructural members to afiix the arm to the waveguide. The box-likemember 13 is removably connected to the supporting arm 14 by the arm 15and the screws 18. Due to the perspective nature of the drawing, onlyone of the springs and the arms are shown in the drawing.

2,876,423 4 Patented Mar. 3, 1959 It is obvious that any suitablesupport mechanism may be employed to hold the box-like member to thewaveguide.

The normal position of the fin 8 is in the slot 7 of the waveguide 6. Itis held in this position by the structure set forth above; however,itmay be desirable to instantaneously change the frequency of thewaveguide to a specific and definite frequency. It may also be desirable to be able to accomplish this change by remote control means. Toaccomplish by remote control this change in frequency, the fin 8 isremoved in this invention by a novel means. The novel removal system forthe fin 8 includes a forceable ejection system. The force able ejectionsystem of this invention is based upon a fuse 16 which, when activated,generates a force suitable to overcome the spring pressure applied tothe member 11. One force which may be used in this invention is theproximity-type fuse similar to the well-known VT fuses used inprojectiles. The fuses 16, there being two in the embodiment of thisinvention for ensuring firing since one fuse is designed with sufficientexpansion or force to overcome the spring pressure, are shown innormally contracted condition in Figure 2. Here is illustrated thespiral cuts which are formed into bellows a portion of the length of thefuse 16. One end of the fuse is a flat surface 17 and the other end ofthe fuse includes two connecting wires 19 which carry the necessarysignals to operate the fuse. The wires 19 are connected to the signalsource through the connection means 23 which are mounted on aninsulating member 20. The fuses which are to be used in this inventiondo not operate upon an excessive current as the normal fuse operates.This fuse operates upon a predetermined signal of some type. This signalmay be either value controlled or possess other distinguishing features.The control signal applied to the wires 19 ignites a small powder chargein the fuse 16 which forceably extends the bellows 16.

Another bellows 16 extended as shown in Figure 1. The flat surface 17 ofthe fuse 16 impresses the force resulting from the explosion of thepowder and the expansion of the bellows upon the plates 21. These plates21 are firmly afiixed to the structural element 11 and the forceresulting from the expansion of the fuses moves the structural member 11and the connected fin 8 against the pressure of the springs 9. Theremoval of the element of the member 11 quickly and positively removesthe fin 8 from the slot of the waveguide 6 thereby changing thetransmission frequency of the waveguide. The fuse 16 require enormouspressures to reform the bellows and must be removed to permit thesprings 9 to return the fin 8 to the slot. The frequency change may beaccomplished by exploding the fuses by signals from the signal source 22thereby providing remote control.

Although this invention has been described with respect to a particularembodiment thereof, it is not to be so limited as changes andmodifications may be made therein which are within the full intendedscope of the invention as defined by the appended claims.

What is claimed is:

1. A system for removing a resistance element from a waveguide includinga waveguide having a substantially rectangular cross section, a slot cutin one face of the waveguide and supporting mechanisms on the oppositeside of the waveguide from the slot, a resistance element generallyconforming to the shape of the slot, means supported on said supportingmeans for retaining said resistance element in said slot, and meansincluding a positive acting explosive fuse in the shape of a collapsiblebellows contained in said supported element for positively removing saidresistance element from said slot whereby the frequency of saidwaveguide is changed.

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."wsy uisie sum n :mwh l ma 9 .1 th Op s s :9; th W mu fmmX- h 5 re anwelement C011- forming tb t he shape of the s1ot, means suppd f te 1 bysaid ,suppgrting meansfor retaining said resistance element in saiglslot and means including a pqsitive acting fuse in the shape'of acollapsible bellows in said "supported eleanelectiical sig'nalfcr femoving said're sistance e letnent e 11L I a c from said wavegulde agamstthe force of said retaxmng means.

References Cited infne file of this patent UNITE -STATES PATENTS

